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LELAND STANFORD JUNIOR UNIVERSITY PUBLICATIONS 
UNIVERSITY SERIES 



The Effect of a Strictly Vegetable Diet on the 

Spontaneous Activity, the Rate of Growth, 

and the Longevity of the 

Albino Rat 



BY 



JAMES ROLLIN SLONAKER 

ASSISTANT PROFESSOR OF PHYSIOLOGY 



WITH ONE PLATE AND FIFTEEN TEXT FIGURES 



STANFORD UNIVERSITY, CALIFORNIA 

PUBLISHED BY THE UNIVERSITY 

1912 




Monognpll 



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LELAND STANFORD JUNIOR UNIVERSITY PUBLICATIONS 
UNIVERSITY SERIES 



The Effect of a Strictly Vegetable Diet on the 

Spontaneous Activity, the Rate of Growth, 

and the Longevity of the 

Albino Rat 



BY 



JAMES ROLLIN SLONAKER 

ASSISTANT PROFESSOR OF PHYSIOLOGY 



WITH ONE PLATE AND FIFTEEN TEXT FIGURES 



STANFORD UNIVERSITY, CALIFORNIA 

PUBLISHED BY THE UNIVERSITY 

APRIL 2, I912 






Stanford University 
Press 



«■ 4 



THE EFFECT OF A STRICTLY VEGETABLE DIET ON 
THE SPONTANEOUS ACTIVITY, THE RATE 
OF GROWTH, AND THE LONGEVITY 
OF THE ALBINO RAT* 



INTRODUCTION. 

The study of dietetics today occupies one of the most important 
places in the field of physiological investigation. Many popular arti- 
cles have appeared in the past few years advocating this or that diet 
as best adapted to the needs of man. The argument is usually based 
on the personal opinion of the writer or the effects a certain diet may 
have had upon him. The personal idiosyncrasies which appear in 
these articles are too numerous to mention. Such writings are of no 
scientific value, and only show the trend of a certain class of people. 

In contrast to these popular articles appear the writing of various 
scientific men giving the results of their investigations. These results 
are based on the comparative digestibility and absorption of the diff- 
erent foods and upon their ability to maintain nitrogenous equilibrium 
in the animal experimented upon. 

The tendency of humanity is to go to the extremes, and nowhere 
is this more manifested than in dietetics. One class, vegetarians, main- 
tains that man should abstain exclusively from animal foods, the other 
class claims that the human alimentary tract is more adapted to omni- 
vorous food than to a strictly vegetable diet. 

Vegetarianism as used by most people is a misnomer. The larger 
proportion of the so-called vegetarians partake freely of such animal 
foods as milk, eggs, butter, cheese and the like. A few, the fruitarians, 
live wholly on nuts and fresh fruits. Another small group live on nuts, 
fruits, legumes and vegetables, either in the raw or cooked state. The 
much larger number of vegetarians (?) live on a mixed diet which dif- 
fers from the ordinary mixed diet in only one respect — the absence of 
meat. 

Most investigators have studied the effects of a certain diet on the 
animal for a limited time, which in most cases is insufficient to warrant 
*From the Physiological Laboratories of Stanford University. 



4 EFFECT OF DIET ON THE ALBINO RAT 

such sweeping conclusions. Because an animal is able to maintain its 
weight and health for a limited time, is no argument that it could do 
so for its entire life. Neither has the effect on the offspring been 
ascertained. Such results can only be obtained by continuing the 
experiment during the lifetime of the animal and succeeding genera- 
tions. 

The present experiment was undertaken to determine as fully as 
possible the comparative effect of a strictly vegetable diet, and an 
omnivorous diet, upon the spontaneous energy of the animal as mani- 
fested by its voluntary activity, the effect on its growth, and on the 
length of its life. An experiment is now under way to study the effect 
on the progeny. No attempt has been made to study the income and 
outgo of nitrogen. 

MATERIALS AND APPARATUS. 

In order that such an experiment may be of value a number of 
similar animals must be used, and the environment of these must be 
the same in every respect, with the exception of diet.^ 

In this experiment sixteen rats were used. To secure these as 
nearly alike as possible, sisters were mated to the same male. After 
numerous trials, lasting more than a year, two sister rats of approxi- 
mately the same size, which had been mated to the same male, gave 
birth to eight each, just a day apart. Previous observations^ have 
shown that the young of a litter of three not only averaged heavier at 
birth than those of a litter of ten, but also gained more rapidly during 
the nursing period and had a better start at the weaning time than 
those of the larger litter. Also the age of the mother had an effect on 
the size of the litter and the average weight of the young. Very young 
mothers were less prolific than older females. 

Minot^ found in his observations on the guinea pig that the aver- 
age 5^oung of a litter of one weighed 85.5 grams, and the average of a 
litter of eight 52.2 grams. Also that the males averaged heavier (71 
grams) than the females (70.2 grams). A similar condition exists 
between the sexes of the albino rat. This difference in weight of the 
two sexes becomes much more marked as the animals grow older. One 
should therefore have rats of the same age, of as nearly as possible 
the same parentage, the same number in the litter, and the same number 
of each sex. Owing to the fact that it is difficult to determine the sex 
of the young rats with accuracy, the sexes were not distributed as I would 
have wished. 

These sixteen young were arranged and designated as follows: 



MATERIALS AND APPARATUS 5 

No. I and No. 2 from litter A, and No. 3 and No. 4 from litter B, were 
put into revolving cages to be used as omnivorous feeders in deter- 
mining their activity; No. 5 and No. 6 from litter A, and No. 7 and 
No. 8 from litter B, were put in revolving cages to be used in ascer- 
taining the amount of work the vegetarian feeders would perform; No. 
9 and No. 10 from litter A, and No. 11 and No. 12 from litter B, were 
put in stationary cages for omnivorous controls; and No. 13 and No. 
14 from litter A, and No. 15 and No. 16 from litter B, were placed in 
stationary cages for vegetarian controls. Thus each litter was equally 
and uniformly distributed. Unfortunately the sexes were not ideally 
grouped. The following table illustrates the manner in which the 
young were distributed. 



Omnivorous Exer- 


Vegetarian Exer- 


Omnivorous Control 


Vegetarian Control 


cised Rats 


cised Rats 


Rats 


Rats 


Litter 


No. 
I 


Sex 


Litter 


No. 


Sex 


Litter 


No. 


Sex 


Litter 


No. 


Sex 


A 


Male 


A 


5 


Male 


A 


Q 


Male 


A 


I,S 


Female 


" 


2 


" 




6 


Female 


" 


10 


" 


« 


14 


Male 


B 


3 


Female 


B 


7 


"■ 


B 


II 


Female 


B 


15 


" 


" 


4 


Male 


" 


8 


" 


** 


12 


Male 


" 


16 





Each rat was thus confined in a cage by itself, which served as 
its home for its entire lifetime, and from which it was taken at inter- 
vals of about two weeks for a time sufficient to weigh the rat and 
clean its cage. 

The apparatus for recording the activity has already been acb- 
cribed,* but may be briefly given again. It consisted of a series of 
eight cylindrical cages which revolved on stationary axles to which 
were attached the nest boxes. The food and water boxes were attached 
to the ends of the nest boxes. The cage thus revolved about the sta- 
tionary nest box whenever the rat ran. Automatic devices were attach- 
ed to register the number of revolutions and to record them on paper 
kept moving by a continuous roll kymograph. The first device being 
read in the morning and in the evening gave the daily and nightly 
run of each rat through its lifetime. The second arrangement showed 
the distribution of the activity of each rat for each twenty-four hours 
during its whole life. These records were of great assistance in show- 
ing the peculiarities of activity which occurred at difTerent ages. 

This apparatus was therefore only adapted to recording the run- 
ning activity of the animals. Previous observations^ have shown that 
the running activity of the rat is proportional to the other activities. 



6 EFFECT OF DIET ON THE ALBINO RAT 

Changes in the amount of the running activity are correct indicators 
of similar fluctuations in the other activities of the animal. 

FEEDING. 

No attempt was made to give a definite amount of protein food in 
the diet nor to try to maintain nitrogenous equilibrium. The diet was 
varied as much as possible, and the amount of food given was more 
than was eaten before the feeding time on the following day. The 
feed and water boxes were then cleaned and a new supply given. 
Cracked corn was always given. The young were weaned at the age of 
28 days and placed in their respective cages, as already described. A 
rich mixed diet, consisting largely of bread and milk with an occasional 
feed of baked beans and meat hash, was given all to prevent any dis- 
astrous effects resulting from the sudden change in environment and 
methods of feeding. This mixed diet was continued for twenty-eight 
days. At this age (fifty-six days) all appeared perfectly healthy and 
normal in every respect. They had each made a normal gain. The 
males averaged 70.1 grams and the females 59.3 grams. 

The difference in the character of the food was introduced at this 
time, the one group being designated vegetarians, and the other, omni- 
vorous feeders. These two groups were fed exactly the same food 
each day, with the exception of meat and other animal foods which 
were given about three times a week to the omnivorous feeders in addi- 
tion to the vegetable food. The vegetable foods were as rich in protein 
as it was possible to obtain from this class of foods, and consisted of 
such articles as the following: fresh vegetables, such as lettuce, kale, 
cabbage, cauliflower, clover and celery; cooked vegetables, such as 
white, corn, brown and graham bread, biscuits, buckwheat cakes, dough- 
nuts, crackers, cookies, oatmeal mush, fried cornmeal mush, dumpUngs, 
corn, rice, baked beans, potatoes, carrots and onions; nuts, fruits and 
grains, such as almonds, English walnuts, apples, cracked corn, wheat, 
and corn meal. Occasionally, when the vegetarians seemed to be losing 
ground too fast, a feed of cheese, milk, or some other animal food was 
given. This was done only a few times soon after the vegetarians 
were first put on their exclusive diet. 

As can be readily seen, the above articles composing the vegetarian 
diet are either found on our tables or can readily be procurred from 
shops. Some of them contained small portions of animal food, i.e., 
graham muffins usually contain an egg and milk, bread often contains 
milk, doughnuts and several other articles contain animal fat. As only 



KIND OF FOOD 7 

very small amounts of animal food were present as compared to a large 
quantity of vegetable food, I have called this a strictly vegetable diet, 
at the same time realizing it is not absolutely such a diet. 

The amount of food given to each rat was not weighed, but meas- 
ured as accurately as possible with a spoon, or by pieces of equal size. 

The following few days' diet taken at random will serve to show 
the variety of food and its frequency. 

April 23. Cooked corn, lettuce, cracked corn and water. 

April 24. Water-soaked bread, almonds, lettuce, cracked corn and water. 

April 25. Baked beans, lettuce, cracked com and water. 

Omnivorous had also meat. 
April 26. Graham muffins, almonds, cracked corn and water. 
April 27. Water-soaked bread, lettuce, cracked corn and water. 
April 28. Water-soaked bread, almonds, cracked corn and water. 
April 29. Cracked corn and water. 
April 30. Mashed potatoes, lettuce, cracked corn and water. 

Omnivorous had also meat. 
April 31. Water-soaked bread, buckwheat cakes, cracked corn and water. 

Another example at another season of the year is as follows: 
Nov. 14. Bread, cracked corn and water. 
Nov. 15. Potatoes, macaroni, cracked corn and water. 

Omnivorous had also meat. 
Nov. 16. Bread, oatmeal mush, cracked corn and water. 

Omnivorous had also meat and bread hash. 
Nov. 17. Water-soaked bread, cracked corn and water. 
Nov. 18. Water-soaked bread, cracked corn and water. 

Omnivorous had also meat and bread hash. 

The amount of meat given to each of the omnivorous rats was 
usually small, consisting of but a few grams. It was given on an aver- 
age two or three times each week. 

We have thus sixteen rats as nearly alike in regard to age, parent- 
age, size and tendencies as it is possible to obtain, subjected to the same 
environments, fed the same food with the exception that the eight omni- 
vorous feeders had a few grams of animal food added to their diet about 
three times each week. It is obvious, therefore, that whatever differ- 
ences may be found between these two groups of rats in regard to their 
activity, rate of growth, and longevity must be due wholly to the pres- 
ence and absence of animal food in the two diets. 



8 EFFECT OF DIET ON THE ALBINO RAT 

ACTIVITY. 

In studying the characteristics of the activity one needs to refer 
to the kymograph records. Figures i to lo inclusive are reproductions 
of such records, and show the activity of each rat for twenty-four con- 
secutive hours at different ages. By comparing these figures a great 
difference is noticed in the activity at different ages. 

Figure i represents the activity of each rat at the age of thirty- 
two days, and just four days after they had been weaned and placed in 
the revolving cages. There is no regularity in the distribution of the 
activity and periods of rest. Neither is there any apparent tendency 
to be more active at one time in the twenty-four hours than at another. 
They were restless, playful and filled with a spirit of investigation. 
Since they were all fed at this time on the same diet, any differences in 
the character of the activity may be attributed to individual variation. 

In Figure 2. which shows the distribution of the activity at the 
age of six months, two important things are noticed. First, the great 
bulk of the activity occurs during the evening and early night time : 
second, the omnivorous rats (O) are more active than the vegetarians 
(V). There is more or less random running for an hour or so before 
and after the feeding time (4 p.m.), but the most is done during the 
night. 

At the age of eleven months (Figure 3) the periods of activity and 
rest are more sharply defined. Also the difference in the amount of vol- 
untary activity of the two classes is very obvious. The activity of the 
vegetarians is approaching closely in appearance that of old age.^ 

In Figure 4 the activity at the age of sixteen months is seen. 
Some days previous to this record the feeding time was changed to 
the morning to see what effect it would have on the distribution of the 
activity. The main bulk is seen to remain constant, but the usual ran- 
dom running which occurs at the feeding time has shifted to the morn- 
ing. At this age two of the vegetarians have died and the other two 
compare very unfavorably with the work of the omnivorous. 

Figure 5, which represents the activity at the age of twenty-one 
months, shows that when the feeding time is returned to the afternoon 
the periods of activity and rest are sharply defined. The omnivorous 
feeders are still quite active when compared to the remaining vege- 
tarians. 

At the age of twenty-five months all the vegetarians were dead 
(Figure 6). The records of the omnivorous rats show a marked ten- 
dency toward old age. Especially is this true in No. i and No. 4. 



0{3*" 



BAM 9 10 (I 12 IPM2 3 4 5 6 7 8 9 10 U 12 1AM 2 3 4 5 6 7 8 

Fig. I. Graphic records sliowing tlie distribution of the activity of each of the 

exercised rats as recorded on the kymograph paper. The rats were ;i2 days 

old and had been weaned and put in their cages but four days before. 

O and V refer to omnivorous and vegetarian rats respectively. 



I7 


' 




' ' ' ' 


'" ' " 






■ 






_ 




o)i 
























u- 






















. 


/5 
























(fi 
























7 














_. 










is 


























8A 


M9 10 


11 12 


If Mi i 4 


5 


6 


7 « 


9 10 U 12 IAM2 


3 


4 


S 6 


7 8 



Fig. 2. Graphic records of activity of omnivorous (O) and vegetarian rats (V) at 

the age of 6 months. 



"li 



I 

(8. 



10 II 12 IPM 2 



Fig. 3. Graphic records of activity of omnivorous (O) and vegetarian rats (V) at 

the age of 11 months. 



( 

S ■ — M nif i m — L-C9 — t gagi n osa »r~i 
_■ 1 T . i i ifln !■ I A^rrn M ■ B — »« I ffi fi * B II 1_ 



3 

(5 

\8 Dead 

^7 Dead 



SAM 9 10 II 12 IPM 2 3 4 5 7 8 10 H 12 lAM 2 3 4 5 6 7 

Fig. 4. Graphic records of activity of omnivorous (O) and vegetarian rats (V) at 

the age of i6 months. 



(6 Dead 
V? 7 Dead 



SAM 9 10 II 12 IPM 2 3 4 A 6 7 8 9 10 II 12 1A^3 2 3 4 5 6 7 

Fig. S. Graphic records of activity of omnivorous (O) and vegetarian rats (V) at 

the age of 21 months. 






V<7 0. 



Dead 
ead 



(8 Dead 

kAM9 10 n 12 !PH 2 3 4 5 6 T « S lO U S lAM 2 3 4 S 6 1~ 

Fig. 6. Graphic records of activity of omnivorous (O) and vegetarian rats (V) at 

the age of 25 months. 



,1 De«<i 



\ fi Pead 
V) 7 Dead 



( 8 Pead 



8AMi> 10 II 12 IPMi 3 4 5 6 7 8 9 10 II 12 lAM 2 3 4 5 b 7 

Fig. 7. Graphic records of activity of omnivorous (O) and vegetarian rats (V) at 

the age of 26 months. 



^ I Dead 



{.4 Dead 



.a Dead 



, a Dead 



V^ 7 Dead 



, a De«<» 



•amII Io ir'""[j Ipiia 3 4 t • t • • io u la uSia s 4 9 e 7~ 

Fig. 8. Graphic records of activity of omnivorous (O) and vegetarian rats (V) at 

the age of 28 months. 



fl Dead 

2, , „ 



O 

i 4 Dead 
( S Dead 
) 6 Dead 



3 



^ )7 Dead 



( B Dead 



BAMS 10 U 12 IPM2 3 4 5 6 7 8 » 10 II « IAM2 3 4 s fi 7 8 

Fig. g. Graphic records of activity of omnivorous (O) and vegetarian rats (V) at 

the age of 31 months. 

'I Dead 



1 2 Dead 

[4 Dead 

V 



S Dead 
6 Dead 



> 7 Dead 



1 8 Dead 



SAM » 10 II 12 IPM 2 



Fig. 10. Graphic records of activity of omnivorous (O) and vegetarian rats (V) at 

the age of 34 months. 



CHARACTERISTICS OF ACTIVITY 9 

The remaining figures (7, 8, 9 and 10) represent the records for 
the ages twenty-six, twenty-eight, thirty-one and thirty-four months re- 
spectively. No. 4 in Figure 7 shows the death struggle of this rat. which 
ended a little before 10 p.m. 

In comparing these different records of activity, one notices that 
in the young rats the periods of activity and rest are of short duration 
and have no definite arrangement so far as the time of the day is con- 
cerned. As the rats grow older the activity becomes greater and 
occurs more and more during the night time, the periods of rest being 
confined to the daytime. This continues until the rats reach the prime 
of life. After some months of almost uniform activity there is a grad- 
ual reduction, and the distribution and amount of work done approaches 
that of youth. It also shows that the vegetarians are not as active, that 
they age more early, and that their duration of life is shorter than the 
omnivorous rats. 

Since all the animals were fed on a mixed diet for twenty-eight 
days after commencing the experiment, any difference in activity dur- 
ing this period must be considered due to individual variation. This 
variation is sometimes very noticeable, as seen in Table I. This table 
represents the average number of revolutions of five consecutive days 
of each rat at the ages indicated. There is not a gradual and regular 
increase in the amount of running done by each, but fluctuations — now 
greater, now less. At first this was thought to be due to making the 
average from too small a number of days. Therefore another table 
(Table II) was made, by taking the average run of each sex of each 
group for a whole month. The figures in the column of the omni- 
vorous males thus represent the average of thirty days' run of three 
individuals. But here again we see the lack of a uniform increase. In 
other words, the activity manifests itself rhythm.ically. No doubt if 
the number of individuals had been greater the results would have been 
more uniform. In a former paper I have discussed the causes of these 
fluctuations.- 

Table II is put in the form of curves in Figure 11. The rhythmical 
variations are very conspicuous. These fluctuations also correspond in 
many cases both in regard to time and appearance. For example, from 
the beginning to the third month there is a rapid rise in the curves, 
showing a great increase in the daily activity. This was, no doubt, due 
to the feed, for they were all fed on a strong mixed diet for almost a 
month, and on rich food for almost two months. The effect of this 
food carried them over apparently till the end of the third month, when 
they began to feel the effects of the lack of it. This was followed in a 
general reduction of amount of daily activity in all except the omnivorous 



lO 



EFFECT OF DIET ON THE ALBINO RAT 





OMNIVOROUS RATS 


VEGETARIAN RATS 


Age N 


0. I 


No. 2 


No. 3 ^ 


fo. 4 No. ; 


, No. 


6 No. 7 


No. 8 


Mos. ]\ 


[ale 


Male 


Female I\ 


/lale Male 


Female Female 


Femal 


J 


I 


348 


1002 


620 


448 118 


2 752 318 


970 




2 I 


200 


1 124 


2118 I 


336 196 


4 668 716 


1952 


3 


790 


886 


1956 I 


832 161 


8 682 1396 


2238 


4 5 


028 


5850 


5782 9406 1 2150 1 542 j 2870 


1468 


5 I 


206 


3930 


7280 


834 42 


657 1206 


3496 


6 


540 


1644 


8482 


540 59 


6 920 I 170 


1472 


7 I 


307 


3144 


IO185 3 


574 108 


4 I 128 3244 


1904 


8 2 


024 


3274 


9518 4 


276 67 


6 565 


2 2400 


3884 


9 6 


002 


7574 


8930 2 


836 83 


6 656 8962 


4106 


ID 2 


618 


4398 


8260 2 


882 85 


8 578 876 


2962 


II 3 


620 


2096 


8640 2 


310 100 


6 340 670 


882 


12 2 


186 


4258 


8902 2 


616 I 144 1 528 1 898 


1004 


13 4 


964 


7066 


11044 3 


084 60 


2 46 1 316 


708 


14 3 


860 


6374 


10992 3 


004 16 


8 ... 


524 


634 


15 I 


428 


4768 


8198 2 


556 9 





918 


96 


i6 I 


006 


2642 


13002 I 


364 34 


2 


68 


96 


17 2 


684 


4776 


5982 I 


998 8 


4 




72 


i8 


744 


2364 


9732 I 


S12 8 


,8 ... 




22 


19 


996 


2476 


8312 


808 y 







60 


20 


806 


2056 


9658 


720 8 


12 




24 


21 


69c 


' 1520 


2210 


482 = 


6 .. 




58 


22 


33^ 


) 1810 


5468 


290 c 


2 




22 


23 I 


6gt 


) 1680 


3188 


456 4 


[O 




88 


24 


38c 


> 1352 


3100 


220 






.... 


25 


9A 


|.* 1466 


4612 


196 












26 . 




188 


2538 


48* 












27 . 




160 


1968 














28 




180 


5171 














29 




72 


2424 














30 




56 


2832 














31 




28* 


1706 














32 






2312 














33 






488 














34 




.... 


435 
60* 















Table I. — Average daily revolutions of the omnivorous and vegetarian rats 
at ages indicated. 

female, which remained practically unchanged. Then, with the except- 
tion of the vegetarian female, there was another general increase up to 
the fifth month. Again, at the tenth month, all show an increase, except- 
ing the vegetarian male, which shows a slight decrease. 

♦The number of revolutions during the 24 hours previous to death. 



DIFFERENCES IN ACTIVITY 



II 





OMNIVOROUS VEGETARIAN 


Age 


Male 


Female Male 


Female 


in 

Months 


(Avg. 3) 


(Avg. I) (Avg. I) 


(Avg. 3) 


I 


73 


102 


68 


53 


2 


689 


724 I 


169 


1040 


3 


2455 


2,944 3 


542 


2017 


4 


642 


3.014 I 


853 


1273 


5 


4375 


6,835 5 


021 


75 


6 


3286 


8,843 


845 


146 


7 


3405 


13.308 I 


242 


1175 


8 


3673 


10,898 I 


211 


2188 


9 


3535 


9,688 I 


057 


2156 


lO 


4717 


11,643 


828 


2316 


II 


3119 


10,136 


998 


905 


12 


2935 


10,513 I 


010 


738 


13 


3957 


9,684 


826 


680 


14 


5081 


11,613 


458 


482 


15 


2285 


9,110 


517 


519 


16 


2247 


8,692 


140 


267 


17 


2069 


9,027 


179 


29 


18 


2262 


7.579 


99 


26 


19 


2212 


9.357 


96 


7 


20 


1599 


9.247 


54 


21 


21 


980 


6,940 


55 


16 


22 


1273 


7.156 


37 


13 


23 


1062 


5.730 


81 


16 


24 


727 


3,664 








25 


746 


3.529 










26 


266 


3.909 










27 


105 


3.774 










28 


149 


3.609 










29 


15 


3.339 










30 


25 


2,808 










31 


10 


1,911 










32 


4 


3.134 










33 


.... 


2,033 










34 





320 









Table II. — Average daily work as indicated by the number of revolutions 
computed by dividing the total run of the month previous by 30. 



It is especially noticeable that the curves representing the two sexes 
of the omnivorous feeders correspond much more closely in their fluc- 
tuations than those of the vegetarian feeders. In fact after the third 
month similarity in the character and time of these fluctuations of the 



12 



EFFECT OF DIET ON THE ALBINO RAT 



omnivorous and vegetarian feeders grows rapidly less and less. The 
same may be said regarding the amount of daily activity of the two 
classes. The omnivorous female far surpasses all others. The omni- 
vorous male comes next in order. Then follows the vegetarian female, 



Revolutions 
14000 



13000 



12000 
11000 
10000 
9000 
8000 
TOOO 



i\ 

t \ 



6000 



3000 




AgwuiMouthit 5 fO /is ' ' 20 25 30 .% 

Fig. II. Curves representing the average daily activity of each sex of the exercised 

rats at the ages indicated. The heavy solid line (OM) is the omnivorous 

males, the heavy dotted line (OF) is of the omnivorous females. The 

light solid line (VM) is the vegetarian males. The light 

dotted line (VF) is the vegetarian females. 

closely followed by the vegetarian male. The females of each class thus 
surpass the males of the same group in average daily activity. 

When we consider the time in life at which these rats do the great- 
est amount of daily running we see, on consulting the curves of Figure 
II, that it occurs in both classes at an early age in life, usually between 
the seventh and twelfth month. In the omnivorous feeders it is a little 
later than in the vegetarians. In a former experiment^ it was ascer- 
tained that the greatest average daily run of the normal male and female 
occurred when they had reached a trifle more than one-third of their 



DISTRIBUTION OF ACTIVITY 



13 



natural lifetime. In this experiment the vegetarians seem to have done 
their best day's work when about one-fourth of their life had passed. This 
was equivalent to about one-sixth of the lifetime of the normal omni- 
vorous rat. 

Let us now consider the total amount of work, as indicated by the 



o 

bfi 

< 

I 
2 
3 

4 
5 
6 

7 

8 

9 

ID 
II 
12 
13 

14 
15 
16 

17 
18 

19 
20 
21 
22 

23 

24 

25 
26 

27 
28 
29 
30 
31 
32 

33 
34 



OMNIVOROUS EXERCISED RATS IVEGETARIAN EXERCISED RATS 



Male 



No. I 



1,200 
18,850 

79,750 

148,460 

248,990 

329,900 

403,070 

487,130 

576,360 

722,880 

817,000 

883,120 

961,360 

1,068,300 

1,165,990 

1,206,980 

1,271,700 

1,309,080 

1,339,080 

1,382,130 

1,400,500 

1,429,570 

1,457,500 

1,469,340 

1,486,250 



Male 



No. 2 



3,050 
26,140 

91,130 

189,620 

322,420 

438,020 

523,320 

650,490 

786,660 

982,210 

1,082,000 

1,215,190 

1,378,680 

1,548,570 
1,666,150 
1,760,900 
1,849,340 
1,975,140 
2,072,520 
2,146,720 
2,203,380 
2,277,120 
2,334,160 
2,380,260 
2,423,250 
2,447,180 
2,456,190 
2,460,110 
2,462,520 
2,463,950 
2,464,770 
2,465,130 



Female 



No. 3 



Male 



1,300 
23,010 
111,320 
201,730 
406,780 
672,070 
1,041,330 
1,388,260 
1,678,890 
2,028,190 
2,332,260 
2,647,640 
2,938,160 
3,286,540 
3,559,830 
3,820,590 
4,091,400 
4,318,780 
4,599,500 
4,867,910 
5,076,100 
5,290,770 
5,462,560 
5,573,480 
5,679,360 
5,796,630 
5,909,860 
6,018,140 
6,118,320 
6,202,570 
6,259,910 
6,353,920 
6,414,900 
6,427,500 



No. 4 



2,060 

23,390 
118,150 
248,780 
409,250 
508,500 
656,470 
777,640 
870,400 
952,860 

1,039,650 
1,104,240 
1,218,620 
1,399,100 
1,389,440 
1,455,930 
1,488,930 
1,529,400 
1,571,080 
1,588,710 
1,601,920 
1,613,700 
1,624,420 
1,631,780 
1,639,060 
1,642,100 
1,642,580 



No. 5 



Male Female Female Female 



2,040 
37,120 
143,380 
198,980 
249,600 
276,960 
314,520 
350,550 
382,320 
407,150 
437,090 
467,380 
492,170 
505,820 
511,340 
515,530 
520,910 
523,000 
525,890 
527,520 
529,160 
530,560 
533,000 



No. 6 



1,180 
26,620 
59,680 
82,070 

98,350 
111,670 
132,580 
158,890 
187,910 
210,720 
224,790 
238,750 
244,370 



No. 7 



760 
22,550 
76,840 

133,430 
180,070 

238,550 
290,780 
374,400 
450,980 
555,180 
581,180 
604,830 
634,340 
651,680 
686,590 
704,900 



No. 8 



2,810 
49,120 

149,330 
238,940 
285,940 
364,240 
406,700 
483,720 
575,160 

659,590 
694,980 
723,820 
749,280 
772,930 
784,740 

787,450 
790,040 

792,390 
793,620 

794,930 
796,360 

797,570 
799,040 



Table III. — Comparative number of revolutions made by the omnivorous 
and vegetarian rats at the ages indicated. The number of revolutions represents 
the amount of voluntary running or work of each rat. 



14 



EFFECT OF DIET ON THE ALBINO RAT 



number of revolutions which each of the exercised rats voluntarily made 
during its lifetime. 

Table III represents the total number of revolutions of each rat 
at the ages indicated. To give a better idea of the amount of work 
equivalent to these revolutions, the actual distance in miles has been 
computed and shown in Table IV. By consulting these tables it is 



OMNIVOROUS EXERCISED RATS 



Age ]V 


lale 


Male 








Mo. N 


0. I 


No. 2 


I 


I 


2.6 


2 


16 


22 


3 


68 


77 


4 


121 


160 


S 


211 


273 


6 


278 


373 


7 


341 


434 


8 


414 


551 


9 


487 


663 


10 


5X2 


832 


II ( 


b9i 


915 


12 


749 


1023 


13 


^il2 


1155 


14 ( 


;)oo 


1318 


IS ! 


586 


1390 


16 i( 


320 


1490 


17 i( 


d8o 


1560 


18 I 


no 


1665 


19 I 


125 


1747 


20 I 


165 


1850 


21 I 


188 


1862 


22 12 


210 


1920 


23 i: 


225 


1980 


24 i: 


244 


2025 


25 i: 


265 


2050 


26 . 




2074 


27 . 




2090 


28 . 




2093 


29 . 




2095.6 


30 . 




2097 


31 • 




2097.7 


32 . 




2098 


33 . 






34 . 







Female 



No. 3 



19 

95 
170 

336 

572 

882 

1181 

1435 
1710 
1980 
2230 
2490 
2780 
3020 

3230 
3460 

3650 
3890 
4125 
4280 

4475 
4620 
4720 
4810 
4900 
5000 
5100 
5180 
5250 
5300 
5350 
5430 
5447 



Male 



No. 4 



1-7 
19.6 
100 
210 
346 
495 
555 
658 
740 
810 
876 

945 
1036 

1115 
1 168 
1220 
1270 
1298 
1325 
1347 
1358 
1362 
1380 
1385 
1389 
1391 



VEGETARIAN EXERCISED RATS 



Male 



No. 5 



1-7 
31-5 
122 

168 
211 
234 
257 
297 
305 
345 
370 
396 

417 
428.6 

433-4 
436.5 
440.6 

444-7 

445-7 

447 

448.5 

449-7 

450.9 



Female Female Female 



No. 6 



I 
22.6 
50.6 
67.6 
83-4 

94-7 
112.4 

134-7 

159 

187 

190.5 

202 

207 



No. 7 



19.I 
65 
113 

153 
200 
246.5 

317-3 
382 

470.5 
492.6 

508.3 

537-7 

552 

581.9 

592.3 



No. 8 



2.4 
41.7 
126.6 
202.5 
242 
309 
345 
410 

487-5 

559 

589 

613 

635 

655 

665 

667 

669.6 

671-5 
672.6 

673-7 
675 
676 
677.1 



Table IV. — Comparative number of miles run by the omnivorous and vege- 
tarian rats in the revolving cages at the ages indicated. 



TOTAL AMOUNT OF ACTIVITY 



15 



readily seen that the work done by all the rats corresponds rather 
closely during the first three or four months. This corresponds close- 
ly to the average daily work shown in Figure 11. As a matter of fact 
the vegetarians average a trifle more at the end of the third month than 





Average number of revolutions 


Average number of miles 


A 


Omnivorous 


Vegetarian 


Omnivorous 


Vegetarian 


Age 
in 


Males 


Female 


Male 


Female 


Male 


Female Male j 


Female 


Mos. 


Avg. of 
3 


Avg. of 
I 


Avg. of 

I 


Avg. of 
3 


Avg. of 
3 


Avg. of 

I 


Avof 
I 


Avg. of 
3 


I 


2,103 


1,300 


2,040 


1,583 


1.8 


1.8 


1-7 


1-3 


2 


22,793 


23,010 


37,120 


32,783 


19.2 


19. 


31-5 


27-5 


3 


95-343 


111,320 


143,380 


93,283 


82. 


95- 


122. 


80.7 


4 


195,620 


201,730 


198,980 


131,480 


164. 


170. 


168. 


127.7 


5 


326,887 


406,780 


249,600 


133,747 


277. 


336. 


211. 


1.59-5 


6 


425,473 


672,070 


276,960 


2.38,133 


349- 


572. 


234- 


201. 1 


7 


527,620 


1,041,330 


314,220 


273,353 


443- 


882. 


257- 


234.6 


8 


638,420 


1,388,260 


3.50.550 


339,003 


.541- 


1181. 


297. 


287.7 


9 


744,473 


1,678,890 


382,320 


403,683 


630. 


1435- 


305- 


342.8 


10 


885,983 


2,028,190 


407,150 


473,163 


751- 


1710. 


345- 


405-5 


II 


979,550 


2,332,260 


437,090 


500,317 


827. 


1980. 


370. 


424-3 


12 


1,067,517 


2,647,640 


467,380 


522,467 


906. 


2230. 


396. 


441. 


13 


1,186,220 


2.938.160 


492,170 


542,663 


lOOI. 


2490. 


417. 


470- 


14 


1,338,657 


3,286,540 


505,820 


556.327 


iiii. 


2780. 


428.6 


471-3 


15 


1,407,193 


3,559-830 


5II-.340 


571,900 


1181. 


3020. 


433.4 


482.6 


16 


1,474,603 


3,820,590 


515,5.30 


578,907 


1243- 


32.30. 


4.36.5 


488.8 


17 


1,536,670 


4,091,400 


520,910 


579,770 


1303- 


3460. 


440.6 


486.6 


18 


1,604,540 


4,318,780 


523.000 


.580.553 


13.38. 


3650. 


444-7 


490.3 


19 


1 ,660,893 


4,599,500 


525,890 


580,763 


1309. 


3890. 


445-7 


490.6 


20 


1,705,853 


4,867,910 


527,520 


581,400 


1454- 


4125. 


447- 


491. 


21 


1,735,267 


5,076,100 


529,160 


581,877 


1469. 


4280. 


448.5 


491.4 


22 


1,773,463 


5,290,770 


530,560 


582,280 


1497- 


4475- 


449-7 


491.8 


23 


1,805,327 


5,462,560 


533,000 


582,770 


1528. 


4620. 


450.9 


492.1 


24 


1,827,127 


5,573.480 








1551. 


4720. 








25 


1,840,520 


5,679,360 














1568. 


4810. 








26 


1,858,510 


5,796,630 














1577- 


4900. 








27 


1,861,673 


5,909,860 














1582. 


5000. 








28 


1,862,980 


6,018,140 














1583- 


5100. 








29 


1,863,450 


6,118,320 














1587.2 


5180. 








30 


1,864,220 


6,202,570 














1587-7 


5250. 








31 


1,864,533 


6,259,910 














1587.9 


5300. 








32 


1,864,653 


6,352,920 














1588. 


5350. 








33 




6,414,900 
















54.30. 








34 




6,427,500 

















5447- 









Table V. — Showing the relative amount of work done by the two classes 
of animals in revolving cages as indicated by the average number of revolutions 
and the average distance run at the different ages. 



i6 



EFFECT OF DIET ON THE ALBINO RAT 



the omnivorous. This is seen by consulting Table V, which represents 
the averages of each sex of these two groups. 

From this I think one of two conclusions may be reached. Either 
the sudden reduction in the rich protein food of the omnivorous rats 
to almost a vegetarian diet (meat being given only two or three 
times a week) has had the effect of checking the activity of all alike, or 
a strictly vegetarian diet at this age is conducive to a slightly greater 
activity. If the latter is true it may be explained in this manner: The 
omnivorous rat had a satisfying diet; the vegetarians did not, and ran 





















^J2W 


•..Mte 






.^■^ 


■ 


•000000 














^m'' 

/" 


















/' 


















/ 


/' 








4000000 










/ 

/ 
















/ 


/' 


















/ 




















/ 

/ 

/ 






































f 
/ 
/ 
/ 

/ 
f 

/ 






^ 






















^/"^ 


















/ 
/ ^^ 


^ 








TEP 








::—- ^^^ 












, ,^ 


^^''"' 
















*«> 


ibiHomlu' ' i 


► ■ • • ' 1 


» ■ ' ' ■ i 


» 


• • • J 


' 


« 


»••■■» 


»■■■■» 



Fig. 12. Curves showing the average total work and the rate it was done of each sex 

of exercised omnivorous and vegetarian feeders. The heavy solid line 

(OEM) represents the work of the omnivorous males, the heavy 

dotted line (OEF) the omnivorous females ; the light solid 

line (VEM) the vegetarian males, the light dotted 

line iVEF) the vegetarian females. 



RATIO OF TOTAL ACTIVITY 1 7 

a great deal, apparently in search for what they desired. The behavior 
of the vegetarians strongly supports this supposition. When they were 
fed they ate ravenously, as if they had been starving. This was not 
so manifest in the omnivorous. It was true that both classes of exer- 
cised rats always appeared more hungry than the control rats of the 
same group. ( 

After the third month the general average of the vegetarians falls 
below that of the omnivorous. This is shown in the curves of Figure 12. 
Here we see that the omnivorous female rapidly surpasses the omni- 
vorous male in the amount of work done. The female vegetarian also 
excels the male of the same class in the distance run, but only to a small 
extent. The females are thus voluntarily more active than the males. 
We also note that the omnivorous male is much more active than either 
sex of the vegetarians. At the time of the death of the vegetarian rats 
(twenty-five months) the omnivorous female had voluntarily dome 
almost nine and one-half times as much work as the female vegetarian, 
and the omnivorous male almost three and one-half times as much as 
the male vegetarian. 

When the total amount of work voluntarily done by each class is 
considered, a still greater difference is observed. The omnivorous fe- 
male ran a total distance of 5447 miles, while the vegetarian female ran 
only 492.1 miles, or a ratio of about 11 : i. The omnivorous male ran 
1588 miles, compared to 450.9 miles for the vegetarian male — a ratio 
of 3.5 : I. The average run for both sexes was, for the omnivorous rats 
3517.5 miles, and for the vegetarians 471.5 miles, or a ratio of almost 

7-5 : I- 

We thus see that when the initiative and ability to do work are 
considered, the result is decidedly in favor of the rats that had received 
animal food in their diet, and overwhelmingly against the vegetarians. 

The curves of Figure 12 show in a general way the rate at which 
the life's work was accomplished by each rat. But to show this more 
clearly Table VI has been constructed. The total average work for 
each sex in the two groups was arbitrarily divided into eight equal parts. 
Then the per cent of average lifetime required to do these fractional 
parts was computed ; also the average age in months equivalent to this 
per cent is given. For example, when the omnivorous male had done 
one-eighth of its total life's work it had lived 16.1% of its average life- 
time, and had reached the average age of 4.5 months. This table shows 
that the males of each group turn oflf their work at a relatively earlier 
age than the females on the same diet. As an illustration, when the 
omnivorous male had done one-half its life work it had lived 36.4% 



i8 



EFFECT OF DIET ON THE ALBINO RAT 



of its life, while the omnivorous female had lived 41% of its life when 
it had accomplished a similar part of its total work. A similar rela- 
tion is seen to exist between the two sexes of the vegetarians. We also 
see that the same fractional part of total work is accomplished at an 



Fractional part of total amount of 
life's work 






Males (3) 



Female ( i ) 



Percentage of life re- 
quired to do work. . 

Age in months re- 
quired to do work . . 



Percentage of life re- 
quired to do work. . 

Age in months re- 
quired to do work. . 



C rt 

.2 Pi 
X 



Male (i). 



Females (3) 



Percentage of life re- 
quired to do work. . 

Age in months re- 
quired to do work. . 



Percentage of life re- 
quired to do work. . 

Age in months re- 
quired to do work. . 



Vs 


M 


Vs 


/2 


Vs 


V4 


I6.I 


21.4 


32.1 


36.4 


46.4 


53-8 


4-5 


6. 


9- 


10.2 


13- 


15- 


19.1 


26.1 


32.3 


41. 


48.8 


53-8 


6.5 


8.9 


II. I 


13.8 


16.6 


19.9 


10. 


12.3 


17.6 


24.1 


32.8 


41.6 


2-3 


2.8 


4- 


5-5 


7-5 


9-5 


15-9 


22.5 


31-9 


42.5 


49. 


53-3 


2.7 


3-8 


5-4 


7.2 


8.3 


9.1 



7/s 

67.9 
18. 

72.6 
24.7 

II.8 

66.1 
II. 2 



Table VI. — Comparison of omnivorous and 
doing their life's work. 



vegetarian rats as to the rate of 



earlier age in the males than in the females of the same class, with the 
exception of the last two items in the vegetarian group : here the male 
is very slightly surpassed by the female. This shows that the male 
ages earlier than the female. That is, when the male has begun to be 
inactive the female of the same age is still quite active. 

We further see that the vegetarians do the bulk of their work at 
an earlier age than the omnivorous rats. That is, they become old, 
decrepit, lack energy and a desire to be active at an earlier age than 
is true in the case of the omnivorous rats. This is true both as to per- 
centage of life lived and age in months. For example, when the omni- 
vorous rats had done seven-eighths of their total work the males had 
lived 67.9% of their life and the females 72.6%, the two sexes averag- 
ing 70%. In the case of the vegetarians the males had lived 51.7% 
and the females 66.1%, or an average for the two sexes of 59%. We 
thus see that the vegetarians had still an average of 41% of their lives 
to live, during which time they did only one-eighth of their work. The 
omnivorous had an average of 30% to live to do the remaining one- 
eighth of their total work. 



RATE OF PERFORMING ACTIVITY 



19 



We have already shown that the ratio of total average work done 
by the omnivorous rats as compared to that of the vegetarians was 
about as 7.5 : i. To make allowance for this, Table VII was construct- 
ed. This shows the percentage of lifetime of the omnivorous rats and 
their age in months which was required to do certain fractional parts 
of the total work of the vegetarians. That is, the two groups are con- 
sidered in respect to their ability to perform the same amount of work. 
The data of the vegetarians is therefore the same in this table as in 
Table VI. From this we see that the average ages in months of the 
two classes correspond rather closely until three-eighths of their work 
was done. After this the ages rapidly differ. When the vegetarian 
male died it was 22.8 months old. The omnivorous male had accom- 
plished the same amount of work when it was but 6.9 months old and 
had lived but 22.5% of its life. The female vegetarian died at the 
average age of 16.9 months. In contrast, the omnivorous female had 
done the same amount of work at the age of 5.6 months, which was 
equivalent to but 16.6% of its lifetime. Or the average total amount 
of work of both sexes of vegetarians was performed at the average 
age of 19.8 months, — that is, their average lifetime. Both sexes of the 
omnivorous feeders had done the same work at the average age of 6.2 
months, which was but 20.9% of their lifetime. 



Fractional part of total amount of 
life's work 


9.8 

2.7 

8.2 
2.8 

10. 

2-3 

15-9 
2.7 


13.8 
3-8 

10.5 
3-6 

12.3 
2.8 

22.5 
3-8 


Vs 


/. 


Vs 


20.5 
5-6 

14.7 
5- 

41.6 
9-5 

53-3 
9.1 


Vs 


Vs 




Males (3) . . 


Percentage of life re- 
quired to do work. . 

Age in months re- 
quired to do work. . 


14.6 

4- 
10.9 

4- 
17.6 

4- 

31-9 
5-4 


157 
4-3 

12.7 
4-3 

24.1 
5-5 

42.5 
7.2 


18.3 

5- 
13.6 

4.6 

32.8 
7-5 

49. 
8.3 


22.5 
6.2 

157 
5-3 

517 
11.8 

66.1 
11.2 


25.2 

6.9 


n 

X 

W 


Female (i). 


Percentage of life re- 
quired to do work. . 

Age in months re- 
quired to do work. . 


16.6 

5.6 




Male (i)... 


Percentage of life re- 
quired to do work. . 

Age in months re- 
quired to do work. . 


100. 

22,8 


t;.2 

bo <J 

w 


Females (3) 


Percentage of life re- 
quired to do work. . 

Age in months re- 
quired to do work. . 


100. 
16.9 



Table VII. — Showing percentage 
required to accomplish the same work 
during the whole of their lifetime. 



of whole lifetime of omnivorous rats 
as that performed by the vegetarian rats 



20 EFFECT OF DIET ON THE ALBINO RAT 

We thus have the same amount of work done by the two classes. 
The vegetarians required 19.8 months, or the whole of their lifetime, 
while the omnivorous needed only 20.9% of their lifetime, and aver- 
aged 6.2 months of age. Thus the ratio of omnivorous to the vegeta- 
rians in regard to efficiency would be 100 : 20.9, or about 5 : i. We 
must not lose sight of the fact that this difiference in ability to do work 
is caused by the presence of animal food in one diet and the absence of 
it in the other, this being the only difference in the environment. 

If a table were made comparing the amount of work done by each 
class at the same average age, the difiference would be more marked 
than just shown. It is not considered necessary to construct such a 
table. 

GROWTH. 

We have just considered what a marked effect on the efficiency of 
the rat these two diets had. Let us now consider the eflFect on growth. 

The rats were weighed before feeding about once each two weeks. 
Weighings made approximately a month apart were selected in making 
Table VIII. This shows the individual weights of each of the sixteen 
rats at intervals of about a month during their entire lifetime. The 
young at the age of thirty days thus appear to be nearly uniform in 
size. The advantage is slightly in favor of the vegetarians, the males 
averaging 42 grams and the females 39 grams, while the omnivorous 
male averaged 41 grams and the female 38 grams. Twenty-eight days 
later, when the two groups were put on the omnivorous and vegetable 
diets, the sexes averaged approximately the same. Eleven days later a 
difiference in the rate of growth is already noticed. This is more 
obvious in Table IX, which represents the averages of each sex in the 
dififerent groups. As the rats became older this difiference in weight 
was more and more noticeable, becoming greater as age advanced. 

It was previously noted^ that the control rats surpassed the exer- 
cised ones in weight. The same is observed here in both groups of 
rats. This is especially noticeable in the curves of Figure 13, which 
represent the data of Table IX. The heavy lines are the averages of 
the omnivorous rats, the light lines the vegetarians. The male in each 
case is decidedly heavier than the female of the same group. Also the 
control and exercised males excel both the control and exercised fe- 
males of the omnivorous group. This relation does not exist in the 
vegetarian. The heaviest omnivorous female exceeds the heaviest vege- 
tarian male by 9 grams and the heaviest vegetarian female by 36 grams. 
The maximum weight in each of these tables is shown in bold type. 



DIFFERENCE IN GROWTH 



21 





Omnivorous 


Vegetarian 


Omnivorous 


Vegetarian 




Exercised Rats 


Exercised Rats 


Control Rats 


Control Rats 




IN 


in 


IN 


IN 




Revolving Cages 


Revolving Cages 


Stationary Cages 


Stationary Cages 


Age 


M 
I 


M 
2 


F 
3 

}s7 


M 
4 
39 


M 
S 
36 


F 
6 

42 


F 
7 
40 


F 
8 

36 


M 
9 
34 


■ M 
10 

45 


F M 
II 12 

39 45 


EMM 

13 14 15 
37 47 42 


M 


MO 


DA 
30 


16 




42 


43 


42 


2 


II 


79 


89 


76 


68 


72 


67 


76 


64 


84 


100 


84 92 


78 96 89 


86 


3 


5 


107 


123 


107 


99 


92 


81 


90 


81 


146 


157 


124 141 


102 121 III 


III 


4 


5 


132 


143 


123 


128 


lOI 


86 


98 


89 


183 


200 


140 178 


109 137 124 


132 


5 


3 


145 


165 


136 


145 


112 


94 


107 


95 


214 


225 


154 205 


125 151 136 


143 


6 


3 


170 


170 


141 


169 


124 


102 


"3 


102 


241 


249 


165 242 


134 160 152 


158 


7 


4 


179 


195 


152 


185 


131 


100 


116 


103 


265 


262 


178 265 


137 164 160 


166 


8 


13 


201 


21Q 


158 


205 


143 


no 


129 


115 


282 


283 


161 292 


145 184 180 


173 


Q 


13 


206 


218 


161 


222 


136 


108 


128 


116 


288 


289 


180 298 


155 185 196 


187 


10 


II 


215 


245 


163 


221 


142 


108 


127 


115 


291 


301 


184 308 


156 181 204 


186 


II 


9 


217 


248 


161 


226 


143 


109 


123 


116 


296 


304 


200 315 


157 182 205 


187 


12 


13 


226 


247 


159 


230 


125 


100 


118 


120 


308 


322 


199 309 


155 163 199 


182 


13 


2 


232 


265 


170 


238 


124 


97 


126 


126 


310 


331 


135 319 


164 . . 2og 


190 


14 


3 


234 


259 


168 


246 


141 




107 


119 


291 


295 


* 296 


151 . . 196 


172 


15 


I 


231 


254 


164 


240 


138 




100 


119 


291 


295 


■• 294 


155 .. 188 


154 


i6 


17 


242 


272 


168 


252 


140 






125 


286 


300 


.. 298 


156 .. 185 


130 


17 


I 


249 


268 


176 


257 


138 






132 


289 


298 


.. 304 


156 .. 177 


107 


i8 


4 


252 


270 


165 


258 


145 






122 


302 


310 


•• 313 


161 . . 168 




i8 


22 


245 


269 


159 


261 


134 






115 


297 


293 


• 310 


152 . . 162 




20 


24 


240 


244 


153 


249 


133 






III 


290 


282 


. . 291 


159 .. 117 




21 


15 
12 


245 
244 

235 


262 


161 


250 

254 
242 


134 

119 

96 






109 

103 

84 


290 

295 
288 


284 
'?8n 


. . 290 
•• 294 
. . 292 


160 . . 




22 


270 
261 


163 
159 






I c;o . . 




23 


7 






270 


147 .. .. 




24 


10 


235 


269 


163 


248 










292 


283 


• • 294 


148 . . . . 




25 


6 


214 


271 


155 


233 










290 


283 


.. 284 


133 • • • . 




26 


fS 




259 

252 


148 
154 


215 










278 
287 


272 


•• 297 
.. 294 


102 . . 




27 


18 












275 






28 


7 




256 


139 












284 


278 


.. 294 






2Q 


7 




251 


147 












293 


270 


.. 302 






30 


15 




263 


157 












288 


268 


• • 300 






31 


7 




264 


163 












288 


263 


.. 304 






32 


5 




206 


151 












279 


269 


•• 302 






32 


20 






145 












271 


258 


.. 285 







33 


9 






159 












264 


252 


. . 280 






33 


26 






128 












259 


251 


.. 277 


1 . . 




34 


26 


















264 


249 


.. 280 






35 


9 


















247 


225 


.. 268 






36 


2 




















242 


.. 277 






37 


10 




















229 


. . 269 






37 


25 




















227 


• • 259 






3« 


18 




















226 


.. 238 






39 


6 




















225 


•• 230 






40 


6 




















220 


.. 225 






40 


24 




















210 


.. 203 






'IT 


IT 




















203 

T85 








'I'l 


t6 


























45 


12 














r ■ 






170 

















Table VIII. — Showing rate of growth of the different groups of rats at 
the ages indicated. The bold figures indicate the maximum weights. Weights 
are in grams. 

*Was killed on account of sickness. 



22 



EFFECT OF DIET ON THE ALBINO RAT 



( 


Dmnivorou 


5 Vegetarian 


Omnivorous 


Vegetarian 


E^ 


.ERCISED R.' 


VTS Exercised Rats 


Control Rats 


Control Rats 


Age in M 


[al< 


J Fern 


ale Male 


Female 


Male Fe 


male 


Mai 


e Female 


Months (A 


V. . 


?) (Av 


I) (Av. I) 


(Av. 3) 


(Av.3) (A 


V.I) 


(Av.. 


5) (Av.i) 


I. 


41 


3 


7 36 


39 


41 


39 


44 


37 


2.4 


79 


7 


6 72 


69 


92 


84 


90 


78 


3.2 I 


10 


10 


7 92 


84 


148 I 


24 


114 


102 


4.2 I 


34 


12 


3 loi 


91 


187 I 


40 


131 


109 


5-1 I 


52 


13 


6 112 


99 


215 I 


54 


143 


125 


6.1 I 


70 


14 


I 124 


106 


244 I 


65 


157 


134 


7.1 I 


86 


15 


2 131 


106 


264 I 


78 


163 


137 


8.4 2 


08 


15 


8 143 


117 


286 I 


61 


175 


145 


94 2 


15 


16 


I 136 


118 


292 I 


80 


185 


155 


10.4 2 


27 


16 


3 142 


117 


300 I 


84 


19c 


156 


11.3 2 


30 


16 


I 143 


117 


305 2 


00 


191 


157 


12.1 2 


34 


15 


9 125 


113 


313 I 


99 


181 


155 


13.1 2 


45 


17 


124 


116 


320 I 


35 


187 


164 


14.1 2 


46 


16 


8 141 


108 


294 


* 


17; 


151 


15. 2 


42 


16 


4 138 


105 


293 




1 65 


! 155 


16.6 2 


55 


16 


8 140 


107 


295 






155 


1 156 


17. 2 


58 


17 


6 138 


no 


297 






145 


156 


18.1 2 


60 


16 


5 145 


106 


308 






14^ 


) 161 


18.7 2 


58 


15 


9 134 


104 


300 






144 


[ 152 


20.8 2 


44 


15 


3 133 


103 


288 






I2C 


) 159 


21.5 2 


52 


16 


I 134 


102 


288 








160 


22.4 2 


56 


16 


3 119 


100 


290 










159 


23.2 2 


46 


15 


9 96 


94 


283 










147 


24.3 2 


51 


16 


3 






290 










148 


25.2 2 


35 


15 


5 








286 










133 


26.6 2 


28 


14 


8 








282 










10 


2 


27.6 2 


27 


15 


4 








285 














28.2 2 


>28 


5 i;? 


9 








285 














29.2 2 


!2; 


M 


^7 








288 














30-5 2 


!3C 


) ic 


7 








285 














31.2 2 


531 


le 


>3 








285 














32.2 2 


Jii 


- 15 


I 








283 














32.7 




i5 


^5 








271 














33-3 




1= 


9 








265 














33-9 


. 


12 


!8 








262 














34-9 


. 












264 














35-3 




. . 


. . 








247 














36.1 




. 










255 














37-3 




. 


. 








248 














37-8 














244 














38.6 






. 








237 














39-2 














234 














40.2 














231 














40.8 














220 














41.4 














218 














44-5 














212 














454 














207 














T- . « 


T-V 


01 


. 























Table IX. — Showing the average growth of the two sexes in the groups 
indicated. The maximum average weight is shown in bold type. The weights 
are in grams. 

*This rat was killed because of sickness. 



DIFFERENCE IN GROWTH 



23 




Fig. 13. Curves representing the average growth of each sex of the four groups of 
rats. The omnivorous feeders are all shown in heavy lines and the vegetarians 
in light lines. Lines of the same character refer to the same sex of similar 
groups. OCM and VCM refer to omnivorous and vegetarian control 
males ; OCF and VCF represent omnivorous and vegetarian control 
females ; OEM and VEM, omnivorous and vegetarian exercised 
males; OEF and VEF, omnivorous and vegetarian exer- 
cised females. 



24 EFFECT OF DIET ON THE ALBINO RAT 

A glance at Tables VIII and IX shows that, with the exception 
of the exercised vegetarian female, the exercised rats reach their maxi- 
mum weight at an older age than the control rats, regardless of the diet. 
In Table X these facts are in a more accessible form. It shows the 
individual weights and the age of each rat, and the average weights 
and ages of each sex in each group, at the beginning of the experiment, 
as the maximum weight, and at death. As already stated, the average 
weights of the young were about as uniform as could be gotten. When 
the maximum weights are considered a marked contrast is noted. In 
every case the average weight of each sex is decidedly in favor of the 
omnivorous rats. 

Considering the exercised rats in regard to the maximum weights 
and weights at death, we find the following ratios: 

MAXIMUM WT. AT DEATH 

Omnivorous male to vegetarian male 1.8 : i 2.2 : i 

Omnivorous females to vegetarian females 1.42 : i 1.36 : i 

In regard to the control rats the following ratios were found : 

MAXIMUM WT. AT DEATH 

Omnivorous male to vegetarian male 1.64 : i 1.9 : i 

Omnivorous female to vegetarian female . . i .22 : i -9 • i 

This last ratio is not reliable, as the control female had to be killed 
on account of sickness. There is no doubt had it been normal it would 
have reached a much heavier weight, since other omnivorous females 
did not reach their maximum weight until a much later age. 

In regard to growth, we must conclude that the data is decidedly 
in favor of the omnivorous rats and against the vegetarians. 

The appearance and attitude of the two groups is also in marked 
contrast. Figures 14, 15, 16 and 17 are photographs of eight of these 
rats, all being of the same age. Those on the left of each figure are 
omnivorous rats ; those on the right are vegetarians. Figure 14 repre- 
sents females. The other three figures are of males. 

These photographs show the marked difference in appearance and 
attitude referred to above. The vegetarians were emaciated and skinny. 
Their back arched and more or less stiffened. The fur was harsh and 
ruflfled, and the tail and nose inclined to be more or less covered with 
dry scale and sores. The attitude presented extreme lassitude and 
indifference. They remained in a crouched position most of the time, 
their legs appearing too weak to support their weight for only a short 
while. They lacked energy and would stay "put" when placed ready 
for photographing. 




Fio- 14 Photographs of omnivorous female (left) and vegetarian female (right) 
" at the age of i year 9 months 16 days. The omnivorous weighed 161 grams, 
the vegetarian 109 grams. 




Fio- 15 Photographs of omfiivorous male (left) and vegetarian male (right) at 
" the age of i year 9 months 16 days. The omnivorous weighed 250 grams, 
the vegetarian 134 grams. 




Fig. 16. Photographs of omnivorous male (left) and vegetarian male (right) at 
the age of i year 9 months 16 days. 




Fi.t 



Photographs of omnivorous male (left) and vegetarian male (right) 
at the age of i year 9 months 16 days. 



RATIO OF GROWTH 



25 



The omnivorous were the reverse in all these respects. They were 
strong, well nourished and supple. Their fur was soft and well kept. 
Tail and nose were clean and smooth. They appeared full of vim and 
energy, it being difficult to keep them quiet long enough to photograph. 
The photographs, though showing a great difference, fail to show the 
marked contrast one would see in a few minutes' observation of the 
two groups. Such an observation would demonstrate the great differ- 
ence in alertness and interest in surrounding objects, quickness and ease 
of movement in response to external stimuli, voluntary movement and 
vigor. The omnivorous appeared in the prime of life in all these 
respects, but in the case of the vegetarians these qualities were mani- 
fested as in extreme old age. 





Young 


At Maximum Weight 


At Death 




d 




,fcc 


Q 
< 


bio 
> 

< 


> 

< 

E 


5 
_bc 


>. 

oi 

.s 

be 
< 


Male Av. 


Fem. Av. 


bO 
< 




Male Av. 


Fem. Av. 




_bf 








be 


819 

685 

1222 


_bfl 




Omnivorous 
Exercised 
Rats 

Vegetarian 
Exercised 
Rats 

Omnivorous 
Control 
Rats 


I 

2 
3 

4 

5 
6 

7 
8 

9 
10 
II 
12 

13 
14 
15 
16 


M 
M 
F 
M 

M 

F 
F 
F 

M 
M 
F 
M 

F 

M 
M 
M 


42 

43 
37 
39 

36 
42 
40 
36 

34 
45 
39 
45 

37 
47 
42 
42 


30 
30 
29 
29 

30 
30 
29 
29 

3C' 

30 
29 
29 

30 
30 
29 
29 


41 
36 

41 

44 


Z7 

39 

39 
37 


252 
272 
176 
261 

145 
IIO 

129 

132 

310 
331 

200 

319 

164 

185 

209 

191 


544 
497 
509 
560 

544 
253 
251 
509 

392 
392 
337 
390 

392 
283 
390 
353 


262 

145 
320 

195 


534 
544 

391 
342 


^76 
124 

200 
164 


509 
338 

337 
392 


214 
206 
128 
215 

96 

97 
100 

84 

* 

247 
165 

135 
172 

150 
163 
117 
107 


746 

925 
IOI4 

785 

685 
381 

463 
682 

1074 
I361 

36ot 
1232 

778 
373 
578 
500 


212 
96 

241 


128 

94 
135 


IOI4 

■508 

360 


Vegetarian 
Control 
Rats 


129 


■484 


150 


778 



Table X. — Showing the difference between the omnivorous and vegetarian 
rats in regard to the age and weight at the beginning of the experiment, the prime 
of life, and the death of each individual. 

* This weight was taken 14 days before death and is therefore heavier than 
it should be. 

fThis rat was killed because of sickness. 



26 



EFFECT OF DIET ON THE ALBINO RAT 



LENGTH OF LIFE. 

The various tables and curves so far given show in a general way 
the comparative length of life of these two groups of animals. A more 
detailed comparison will be necessary. 

In Table X the age of the death of each rat is given, also the 
average age of each sex comprising the various groups. When the 
same sex is compared it is noticed that the omnivorous feeders surpass 
the vegetarians in longevity by a good margin. The only exception was 
No. II, which should not be used in these comparisons as it was killed 
on account of sickness. When the averages are compared the contrast 



(>* 








■ 


- 








«e 










/H 












V8 










o» 








•*\r 




. 












••{: 




















■ 


IMI 2 


M 4 


» • 


ra » 


K> " Hw 


II»» 





Fig. i8. Diagram representing the average age of each sex of the four groups. OE 

omnivorous exercised; VE, vegetarian exercised; OC, omnivorous controls; 

VC, vegetarian controls. M and F refer to male and female. 

is still more pronounced. These averages are put in diagramatic form 
in Figure i8. The horizontal lines represent the average age at death 
of each sex in the different divisions. 

OE, VE, OC and VC refer to omnivorous exercised, vegetarian 
exercised, omnivorous control, and the vegetarian rats, respectively. 
The relatively short duration of life of the vegetarians is very conspic- 
uous. 

If the average lifetime of all the omnivorous males is compared 
with the average of all the vegetarian males, we find a ratio of 1020 
days to 534 days; or 1.91 : i. When the females are similarly com- 



O ; 

V 



Days aOO 400 600 800 lOOO 1200 

Fig. 19. Diagram showing the average lifetime of all the omnivorous rats (O) and 

all the vegetarians (V). 

♦This rat was killed at this age because of illness. 



LENGTH OF LIFE — APPLICATIONS 27 

pared the omnivorous averaged 1014 days, and the vegetarian 574 days, 
or a ratio of 1.77 : i. If the average of all the omnivorous, including 
both sexes, is compared with the average of all vegetarian rats we 
have the relation of 1020 days to 555 days, or a ratio of 1.84 : i. 

Figure 19 shows in graphic form the total average lifetime of the 
omnivorous rats (O) and of the vegetarians (V). The first group 
lived almost twice as long as the last. This is a decided diflFerence. 
When we recall that all these animals were of the same age and as 
nearly as possible the same parentage, were subjected to similar envir- 
onment, and fed exactly the same food, with the exception that the 
omnivorous group received animal food in addition about three times a 
week, we must conclude that this great difference is due to the presence 
of this animal food and to nothing else. 



GENERAL APPLICATIONS AND COMPARISONS. 

Any attempt to make a practical application of these results to 
man, will no doubt be severely criticised by some on the ground that 
what is true of the albino rat would not hold true in man, owing to the 
wide difference in zoological position. Such a criticism would be based 
on the prevalent idea that man is a supreme being, occupying a place 
above animals, and with which he is not to be compared. 

The rat is by nature an omnivorous animal. All evidence points to 
the fact that man is by nature an omnivorous animal. The cftaracter 01 
the teeth and the digestive tract throughout are best adapted to a 
mixed diet. His nearest related kin in the animal kingdom — the an- 
thropoid apes — are all omnivorous feeders. In his savage state he par- 
takes of the food most accessible, which includes animal food whenever 
it is possible to secure it. There is probably no animal as capable of 
adapting itself to so great changes in environment and in diet as man. 
But though he is able to adapt himself to a restricted diet, is such a diet 
capable of developing and maintaining his maximum mental and phy- 
sical energy for a long period of life? It is not a question of what 
food will keep the animal alive, but what diet will make it the most effi- 
cient machine. It is not so much a problem of determining what foods 
are necessary to maintain nitrogenous equilibrium in man, as it is of 
ascertaining what diet is necessary not only to prolong mental and 
physical efficiency during a long period of life, but to produce initiative 
in these respects. 

The rats fed on the mixed diet had by far the greater initiative and 



28 EFFECT OF DIET ON THE ALBINO RAT 

ability for muscular work. The mental ability was not tested, but one 
would judge from their appearance and alertness that they would far 
surpass the vegetarians in this respect. 

A perusal of the literature of this subject convinces one of the fact 
that the results of the experiments on the rat can be applied to other 
animals, including man. 

Jaffa,® in his investigations on a family of fruitarians, says that 
the youngest child which had lived from infancy on nuts and fruit "was 
certainly undeveloped. Her bones were very small, although she had 
no tendency toward rhachitis. She looked fully two years younger 
than she was." The diet was not satisfying and the craving for other 
foods was occasionally satisfied by eating them. All the family were 
below size. 

Chittenden''^ fed dogs on vegetable foods and animal fat with dis- 
astrous result. In referring to this he says : " This is by no means 
an exceptional case, but we can cite many examples of like results 
where the animals when restricted to a purely vegetable diet, such as 
bread, pea-soup, bean-soup, etc., re-enforced by an animal fat, quickly 
passed from a condition of health into a state of utter wretchedness, 
with serious gastro-intestinal disturbance." 

Caspari,^ in studying the effect of a vegetarian diet on man, found 
that he could not maintain his body weight, but lost 13 K during the 
experiment. Milk and butter had to be added. In another person 
he found that he could maintain his weight on a vegetable diet. He 
was, however, very thin, and the amount of protein in the faeces was 
large. These experiments lasted for only a short time. 

Langworthy," in discussing food and diet in the United States, 
says : "In general, the food habits of the human race today are an 
expression of the thousands of years of experience in which man has 
sought to bring himself into harmony with his environment, and food 
habits have been determined, as regards materials selected, by avail- 
able supplies, man being by nature omnivorous." Man likes variety. 
People of the United States are well nourished compared with other 
races. He further says : "The acknowledged energy and achievements 
of the American people, together with their general good health and 
physical well-being, certainly indicate that we have in the main used 
our food resources advantageously." 

In regard to the digestibility of animal and vegetable foods, we 
find investigators pretty closely agreeing in their results. Albu,^" in 
metabolism experiments on a vegetarian, found that only ^Jjo of the 
protein and 65% of the fat of this food was digested. Snyder,^^ in 



GENERAL APPLICATIONS AND COMPARISONS 29 

discussing the comparative digestibility of animal and vegetable pro- 
tein, says that 95% of the former and 85% of the latter are digested. 
Benedict,^- in comparing the digestibility of animal proteins and fats, 
found that 97% of animal protein is digested and 84% of vegetable 
protein. In a mixed diet he found that 92% of the protein was digested. 
In regard to fats he found that 95% of animal fat was absorbed and a 
less amount of vegetable fat. Many other investigators have found that 
vegetable protein is not used by the body to the same extent as animal 
protein.^^ ^* 

In regard to the effect of diet upon activity, Thompson, ^^ in his 
studies on dietetics, says : "Meat in general has a more stimulating 
effect upon the system and is more strengthening than vegetable food, 
and it gives rise to the sensations of energy and activity." A person^' 
who changed from a mixed diet to a vegetable one, in describing the 
effect says : " I, too, felt chilled and sleepy by day and night, so tired 
that I could hardly walk." This describes the general appearance of 
the vegetarian rats very closely. Nitti,^^ in accounting for the greater 
efficiency of the Italians in the United States than in Italy, attributes it 
to the fact that their diet here is richer in protein, containing a greater 
proportion of meat. 

In regard to the amount of protein required, most of the results 
again are in close accord. 

Caspari^^ concludes that the minimum amount of protein required 
varies with different individuals, and may also vary in the same individ- 
ual within wide limits. This is shown in the dietary study^^ of Sandow, 
the " Strong Man," who consumed 244 grams of protein each day. 
This is far above the average. 

Chittenden (7) has demonstrated that man can maintain his nitro- 
genous equilibrium on a diet containing far less protein than the 
average diet. He has not, however, carried this far enough to deter- 
mine what effect such a diet would have on the life of the individual 
or the race. 

Shutt-" found that in hogs fed on a low protein diet — corn only — 
the meat was inferior and soft. When additional protein was added 
in the form of milk, the meat was greatly improved. He also states that 
hogs fed on too high a protein diet had inferior meat. These results 
were confirmed by Skinner.'^ He adds that hogs fed on corn meal 
have " poor appetite, light bone, deficient development in valuable por- 
tions of the carcasses, and a general state of unthrift, as shown by the 
hair, skin, and hungry look of the animal." When one-sixth of the 
amount of normal ration rich in protein was added the hogs had normal 
growth and were in healthy condition. 



30 EFFECT OF DIET ON THE ALBINO RAT 

Haecker^^ experimented on two groups of cows, the first group 
having a normal amout of protein and the second group a low amount. 
No difference was noticed at the end of the second year, except that 
the second group weighed less. Soon after this time the second group 
began to decline. They grew thin, hair became harsh, and their con- 
dition became generally poor, showing under-nutrition. The amount 
of protein had to be increased in order to preserve their lives. Here 
we see that this group did well for two years before any serious effects 
were manifested. A similar result was found in the rats experimented 
upon. The rats first showed a difference in weight. Later at the age 
of three or four months changes in the activity and general condition 
began to appear. One is not warranted, therefore, in drawing sweep- 
ing conclusions of the effects of certain diets on any animal from a few 
weeks' or months' experimentation. 

McCay^^ studied the effect of the native diet, low in nitrogen and 
rich in non-nitrogenous foods, on the physical condition, the health and 
the efficiency of the Bengalis, compared to European diet and Euro- 
peans in the University of Bengal. From the data of body weight, 
height and chest measurement of 2,500 Bengali students he concludes 
that the Bengalis "do not reach the same standard of general physique 
as is attained by races of European origin ; and yet from the evidence 
we can find no cause inherent in the Bengali as a race for this deficiency ; 
on the contrary, we consider that there may be a very close relationship 
between the lower physical development of this people and the meager 
protein contents of the diet on which they subsist." In comparing 
growth of the Bengali and European students he says : " The two 
classes enter college about the same age, live in the same climate and 
under very similar conditions . . . but the results at the end of their 
college career are very different. The European boys develop into 
strong, healthy men quite up to the average of European standards, 
while the Bengali students almost remain stationary as regards devel- 
opment." He finds that the Europeans are much more capable of en- 
durance. 

Watson and Hunter^ have shown that when young rats are fed 
on a diet of rice the growth is arrested and death results in two or 
three months. When fed on a porridge diet made by boiling together 
oatmeal, milk, water and salt the growth was arrested and death result- 
ed within four months. They were evidently not able to assimilate this 
food even though it was reasonably rich in protein. When fed a strict- 
ly flesh diet the results were disastrous in most cases when the rats were 
very young. When rats two or three months old were put on an 



GENERAL APPLICATIONS AND COMPARISONS 3I 

exclusively ox-flesh diet the result was favorable, growth being pro- 
moted, the anmials reaching a larger size than the normal control rats. 

In regard to races of men it is interesting to note that those whose 
stature is large partake freely of meat, while those of small physique 
live largely on a vegetable diet. 

Oshima^^ says in regard to the Japanese : "Among the ordinary 
families in the rural district the use of meat is (of necessity) restricted 
chiefly to festive occasions ; and among the poorer peasantry even rice is 
used at such times." He further says that the poorer classes of cities and 
country, comprising about 75% of the total population, are vegetarians 
from force of financial circumstances rather than from principle. They 
eat animal food whenever they can get it. This usually consists of fish 
two or three times a month, and meat two or three times a year. 

Boas-*^ found that the North American Indians living on the moun- 
tains are smaller than those living on the plains. He attributes this to 
greater abundance of rich food on the plains. 

Sill,^^ in his study of malnutrition of the school children in New 
York City, found that out of 210 cases, 83% practically depended on 
vegetable food, consisting largely of bread, tea and coffee. 

Albertoni and Rossi"^ found that when meat was added to the diet 
of the peasants of the Abruzzi region, who had been almost exclusively 
vegetarians for generations, there was an increase in power of assimi- 
lation, in body weight, and in physical power. 

Houssay,-" in his experiments on chickens fed exclusively on ani- 
mal and vegetable rations, found that the chickens fed on animal food 
grew much faster than those fed on vegetable rations. This corres- 
ponds closely to my experiments on the rats. 

These results correspond closely with those of Bolte.^° He fed 
chickens on a number of rations, and concludes : " In the absence of 
skim milk to mix with the grain, some other animal concentrate should be 
supplied. A ration containing 10% of animal meal gave a much 
greater gain than rations containing either no animal meal or 20% 
animal meal. The cost of feed per pound of gain was lessened one- 
third under the same condition. 

In regard to therapeutics, diet has a great value. 

Rubner,^^ in his studies on the diet of the poor who have lived 
largely or wholly on vegetables, concludes that this diet is the cause of 
lack of physical condition and ability for work; that it causes an in- 
crease in morbidity and mortality by lowering the ability to resist epi- 
demic diseases. 

In the treatment of tuberculosis it has been found^^ that food with a 
rich protein content is of great value. 



32 EFFECT OF DIET ON THE ALBINO RAT 

McCay-^ finds that kidney disease is much more prevalent in native 
inhabitants of Bengal than in Europeans who live there. He attributes 
this to their diet, which is low in protein. 

Thompson/^ in regard to power of vegetarians to resist disease, 
says : " In regard to an exclusive or almost exclusive vegetable diet 
for man, the universal experience has been that while it may keep him 
in apparent health for some time, it eventually results in a loss of 
strength and general resisting power against disease, which becomes 
evident after some months, if not before .... Animal food in 
some form must be regarded as absolutely essential for all vigorous 
races." 

It is claimed that vegetarians convalesce more slowly after a period 
of illness.^^ That animal food makes blood richer in red corpuscles 
and gives firmness to muscle without excess of fat."* 

In 1883, when the diet consisted largely of rice, 33% of the Jap- 
anese marines had beri beri. In 1884 meat and bread were added to 
the rations, and now they hardly have three cases a year." 

When the effects of a restricted diet and of various diets upon the 
resistance of animals to certain poisons are considered, Hunt'* has found 
that " diet has a marked effect upon the resistance of animals to certain 
poisons; the resistance of some animals may be increased forty-fold by 
changes in diet. • Certain diets, notably dextrose, oatmeal, liver and kid- 
neys, greatly increase the resistance of mice to acetonitril ; their effect is 
similar in this respect to the adminsitration of thyroid. The experi- 
ments show that foods such as enter largely into the daily diet of man 
have most pronounced effects upon the resistance of animals to several 
poisons. They produce changes in metabolism which are not readily 
detectable by methods ordinarily used in metabolism studies. The ease 
and rapidity with which certain changes m function are caused by diet 
are in striking contrast with the essentially negative results obtained by 
the chemical analyses of animals fed upon different diets." 

Hutchison^^ claims that intellectual capacity and bodily energy are de- 
pendent on a mixed diet, and that " it is not without reason that the 
more energetic races of the world have been meat eaters." 

A study of the dietaries of the various races of the world con- 
firms this. Wherever we find advancement in civilization, great achieve- 
ments in the arts and sciences, maximum mental and physical ability, 
thrift and success, we find that animal food has formed a prominent 
portion of the diet. 

The numerous observations and experiments on man and other 
animals in regard to the effects of an exclusive vegetable diet, as com- 



GENERAL APPLICATIONS AND COMPARISONS 33 

oar.d to a mixed diet, upon tlie general condition of the animal, all 
ag ee They show that the vegetable diet produces far -f-or results 
n almost every respect. Man does more work on a mixed diet than he 
did on a vegetable diet or almost exclusive vegetable diet. Man at 
ufns a griat'er stature on a mixed diet rich in protein than on veg - 
talk food Man has made more advancement and achieved more mtel- 
ectuaUy and physically on a mixed diet than on a vegetable one. He is 
abk to'mat'ain his 'body weight and physical well-bemg best on a 

""Ihf results of the experiments on the albino rats correspond so 
closely with those on man and other animals that one is almost justified 
rconcluding that if man were subjected to the same conditions of food 
for h"s Ufetfme the results in regard to voluntary activity, growth and 
longevity would be the same. 



CONCLUSIONS. 



'^^t ThTom^c:o;s feeders are much more active -d voluntari^ 
do much more work during their lifetime than the vegetarians. The aver 

''' f Thi ""Lpfs; the males of the same group in activity. 
This differenceTs greater in the omnivorous than in the vegetarian rats. 

'-^"'r C'tot:fwork"mplished by the vegetarians during their 
Ufe taJ perfo^ed by the omnivorous rats when but .0.9% of their 

""^5'1hrv"eje::rian rats age much earlier in life, it r^^r^^^^ 
half thdr lifetime to perform the last one-eighth of their hfe s work, 

compared to three-tenths for the °"i"'™™f J^^^ ^^^^^j^,, The ra- 
\. The growth of the vegetarians w s gr a ly « -d^d^^^^^^^^^^ 

tio of maximum weights was as 1.62 .1 in tavor 



feeders. 



34 EFFECT OF DIET ON THE ALBINO RAT 

7. The effect on general conditions of the body was most over- 
whelmingly in favor of the omnivorous. The vegetarians were frail, 
weak, and showed extreme lassitude and indifference. The omnivorous 
were the reverse in all these respects. 

8. The average life of the omnivorous was 1020 days, that of the 
vegetarian 555 days. This was a ratio of 1.84 : i. 

9. The control rats in stationary cages lived longer than the exer- 
cised rats of the same group. 

10. All of the omnivorous rats surpassed the greatest age attain- 
ed by the oldest vegetarian rats. 

11. From numerous observations and experiments of other inves- 
tigators on man we would infer that similar results would obtain if he 
were subjected to similar conditions throughout his lifetime. 



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36 EFFECT OF DIET ON THE ALBINO RAT 

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